1. Field of the Invention
The invention relates to a metal shielding can, more particularly to a metal shielding can for shielding electromagnetic waves generated during operation of an electronic component, and an assembly of the metal shielding can and a circuit board.
2. Description of the Related Art
Referring to FIGS. 1 and 2, to solder metal shielding cans 12 (see FIG. 4) onto a circuit board 11 of a handheld electronic device, such as a mobile phone, a personal digital assistant, etc., a steel plate 13 is generally placed and positioned on the circuit board 11. Since the steel plate 13 is provided with loop-shaped passages 131, when a coating mechanism (not shown) applies a tin paste 14 onto a top face 132 of the steel plate 13, the tin paste 14 will fill the loop-shaped passages 131 and will be transferred onto solder pads 111 of the circuit board 11. Subsequently, referring to FIGS. 3 and 4, the steel plate 13 is removed from the circuit board 11 to permit mounting of electronic components 15 respectively on the circuit board 11 in areas confined by the tin pastes 14. Finally, the metal shielding cans 12 are respectively placed over the electronic components 15 on the circuit board 11 at the positions of the tin pastes 14, and the circuit board 11 is transported to a reflow furnace for solder reflow to enable the metal shielding cans 12 to be soldered to the circuit board 11.
To conduct repairs or replacement of a damaged electronic component 15, the corresponding metal shielding can 12 must first be removed from the circuit board 11 using a rework machine so as to allow a subsequent repair or replacement operation to be performed. After the repair or replacement operation, the corresponding metal shielding can 12 needs to be re-soldered to the circuit board 11. Since there are many other electronic components 15 already mounted on the circuit board 11, transfer of the tin paste 14 using the steel plate 13 is no longer feasible, and it requires an operator to apply the tin paste 14 to the circuit board 11 manually. However, it is not easy to control the precision of the position of the applied tin paste 14 as well as the amount of the tin paste 14, which may result in the problem of solder overflow after the metal shielding can 12 is placed on the circuit board 11 at the position of the tin paste 14, and may even have an adverse effect on the electronic component 15. Furthermore, referring to FIG. 5, after the tinpaste 14 has solidified, a barrier portion 141 is formed at each of inner and outer side surfaces 121, 122 of the metal shielding can 12 so that, when the metal shielding can 12 is subjected to an external force (F1) or (F2) (i.e., a shear force) acting in a horizontal direction, the force (F1) or (F2) can be countered by the barrier portions 141 so as to prevent disengagement of the metal shielding can 12 from the respective solder pad 111. However, the provision of only the barrier portions 141 at the inner and outer side surfaces 121, 122 may still result in loosening of the metal shielding can 12 after long-term use.
On the other hand, a metal shielding can disclosed in Chinese Patent No. ZL200420090137.2 includes a conductive case and a conductive cover plate assembled to the conductive case. The disclosed metal shielding can is relatively costly to manufacture, and is primarily provided to overcome problems of leakage of electromagnetic waves between the conductive case and the conductive cover plate.